Check for phi-uses of arguments object before eliminating dead phi's.

Check for phi-uses of arguments object before eliminating dead phi's.

HGraphBuilder::TryArgumentsAccess does not emit any uses for receiver and will generate incorrect code when receiver for a property access is defined by a phi that returns either arguments object or something else.
 
BUG=v8:1582
TEST=test/mjsunit/regress/regress-1582.js
Committed: http://code.google.com/p/v8/source/detail?r=8774

[Kevin Millikin (Chromium), 2011-08-02 09:21:25]

LGTM.

http://codereview.chromium.org/7553006/diff/1/src/hydrogen.cc
File src/hydrogen.cc (right):

http://codereview.chromium.org/7553006/diff/1/src/hydrogen.cc#newcode2315
src/hydrogen.cc:2315: Bailout("Unsupported phi-use");
1.  There should be a unique bailout reason (to distinguish from the later one),
I suggest "Unsupported phi use of arguments object" here and "Unsupported phi
use of uninitialized constant" later.

2. You could consider moving the calls to Bailout into the CheckPhis/CollectPhis
functions, make them void functions, and call them like:

graph()->CheckPhis();
if (HasStackOverflow()) return NULL;

I'm not sure if I like that better.  What do you think?

[Vyacheslav Egorov (Chromium), 2011-08-02 09:26:23]

Thanks.

http://codereview.chromium.org/7553006/diff/1/src/hydrogen.cc
File src/hydrogen.cc (right):

http://codereview.chromium.org/7553006/diff/1/src/hydrogen.cc#newcode2315
src/hydrogen.cc:2315: Bailout("Unsupported phi-use");
1. Done.
2. I don't think HasStackOverflow is pretty enough I will keep bailout here.

On 2011/08/02 09:21:25, Kevin Millikin wrote:
> 1.  There should be a unique bailout reason (to distinguish from the later
one),
> I suggest "Unsupported phi use of arguments object" here and "Unsupported phi
> use of uninitialized constant" later.
> 
> 2. You could consider moving the calls to Bailout into the
CheckPhis/CollectPhis
> functions, make them void functions, and call them like:
> 
> graph()->CheckPhis();
> if (HasStackOverflow()) return NULL;
> 
> I'm not sure if I like that better.  What do you think?